A thin film transistor (TFT) is an important constituent part of a liquid crystal display (LCD). The TFT comprises a base, and a gate electrode, a gate electrode insulating layer, an active layer, a source/drain (S/D) electrode and an insulating protective layer which are laminated on the base in sequence.
A material with small resistance and high conductivity, for example, Cu or Al, is usually selected as the material of an electrode (the gate electrode or S/D electrode) in the TFT, such that the power consumption and the voltage drop are reduced and a response speed is improved. By taking Cu as an example, when Cu is adopted to manufacture the electrode, a layer of Cu is deposited at first, then a photoresist pattern is formed on the layer of Cu, and then the part not shielded by the photoresist pattern is etched by adopting an etching liquid to obtain the electrode. However, in one aspect, since Cu is high in conductivity, there exists a thinning requirement when the electrode is manufactured. In order to manufacture the electrode with a smaller width, during etching, the corresponding photoresist pattern is also thinner. In addition, a binding force between Cu and the photoresist is not high enough, and as a result, the photoresist is easy to strip. In another aspect, the etching liquid adopted for etching Cu is small in viscosity and can easily enters a space between the photoresist and Cu. For the reasons in these two aspects, the etching liquid may etch Cu in a position without a need of etching. Besides, Cu is more active and can be easily oxidized when making contact oxygen and water, which affects a contact resistance between the electrode and other film layers.
Therefore, when Cu or Al is adopted to manufacture the electrode, the problems of how to prevent the etching liquid from etching Cu or Al in the position without the need of etching and how to avoid oxidation of Cu or Al, etc., are especially important.